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Clock
Background The final circuit incorporates all the other circuits and integrates them into one system. The 60 Hz Clock is used to provide a signal to the Counter Circuitry, which outputs a minutes and hours count to the Registers. The output from the registers is sent to the Multiplexers. The Multiplexers select which register it will take a bit from, and sends that bit to the 7 segment display board. The 1 kHz Clock is used as the clock for the registers, multiplexers and the counter/ decoder circuitry that selects which display to turn on. This counter/decoder circuitry works by the counter sending a 2 bit pattern, from 0-3 which is sent to the decoder. The decoder then outputs a low on the selected output and a high on the other 3 outputs. Since the display board needs 1 high and 3 low inputs to turn on 1 display, this pattern is inverted before being sent to the display board. System Design As mentioned in the background, all previous parts were integrated all together to produce a working digital clock. The time is ran by a 60 Hz clock which is being produced from a 555 timer. The 60 Hz runs a divide by ciruitry, this allows the frequency to be divided by 60 to produce a pulse every second. This pulse is further divided by 60 in order to produce a pulse 1/60 cycles which would be used to count minutes. This is then divided to produce a pulse 1/3600 cycles to pulse for the hours. The divide by circuitry is connected to the buffers. The buffers store the count and allow the multiplexer to read in the value and display it on the selected 7-segment display. Test Plan/ Troubleshooting When integrating the clock, we ran into a few problems. A major problem that was encountered was the GAL chip that was apart of the 7-segment display got fried due to a short circuit. The wires were connected to the wrong input/output. Finding the short was a hard task as there weremany wires and following them became difficult. We solved the issues by usuing another GAL chip and eventually realsing that the 60 Hz clock did not have its power and ground connected. This second GAL chip also had to be reprogrammed. Once the clock was running we decided to run it for a few hours to see how accurate it was . We started the clock at midnight, Wednesday and the next morning it was displaying 7:36 when it was 7:30, so it was faster and wasn't telling the correct time. To fix this, we lowered the requency because it had a frequency of 61/62 Hz, we dropped the frequency to around 58-60 Hz. Then it was left on over Thursday night to determine accuracy Test Results Conclusion In Conclusion, the finished clock worked. It was fairly accurate. Some recommendations that we would suggest, is use the schmitt trigger for the 60 Hz clock as it is more stable, and would produce a more constant frequency which is necessary to run the time counting portion of the circuitry. Also, having a better colour coding system would be another recommendation. This saves a lot of time when debugging or trying to find a problem. We also should have also made the full circuit multisim file actually function. As it is, it does not function because the GAL chip does not actually have any properties to it, Having a full multisim circuit to try out ideas to incoroporate 12-24 h functionality and setting the time would have been helpful.